The present invention relates generally to digital multimeters. More particularly, the invention relates to a digital multimeter having a remote display with automatic communication mode switching.
Digital multimeters (DMMs) function to measure a number of electrical parameters as needed for service, troubleshooting and maintenance. Such parameters may include AC voltage and current, DC voltage and current, resistance and continuity. In some cases, a DMM may measure other parameters such as capacitance and temperature.
A DMM will often be configured as a hand-held unit having a rotary knob by which various functions are selected. A plurality of lead jacks are provided in the case (i.e., housing) of the unit for connection of test leads. The specific jack used may depend on the function that has been selected. An LCD display provides a reading of the tested parameter. Details regarding the construction and operation of multimeters may be discerned from U.S. Pat. Nos. 7,034,517, 6,466,003 and 6,043,640, each of which is incorporated herein by reference in its entirety.
Generally, it is desired to place the DMM on a flat surface such as a shelf as measurements are being conducted. Often, however, the shelf may be in a position making it difficult to view the LCD display. In this circumstance, the user may be required to look away from the point of measurement in order to see the measurement reading. A remote display, separate from the DMM but linked by communication to the DMM, may be used to lessen this difficulty. Examples of remote displays are shown in U.S. Pub. No. 2003/0137310 to Holzel and U.S. Pat. No. 7,304,618 to Plathe.
The remote display may use wireless coupling, such as infrared (IR) or radio frequency (RF), for communication with the DMM. While IR and RF are both effective, each has its limitations. RF utilizes a relatively high level of power, thus reducing battery life at the remote display. IR uses less power, but requires a line of sight between transmitter and receiver.